Piezoelectric ceramic compositions



Feb. 4,1969 HIROMU OUCHI ET AL 3,425,944

' PIEZOELECTRIC CERAMIC COMPOSITIONS INVENTORS HIROMU OUCHI MASAMITSUNISHIDA Feb. 4, 1969 H|RQMU ouc ET AL 3,425,944

\ PIEZOELEOTRIC CERAMIC COMPOSITIONS Filed Dec. 14, 1965 Sheet 2 PIC?)I.OwI.%NiO

-& 03 O O QUALITY 2000 Cg; \a.

COUPLING COEFFICIENT. Kp% I N FACTOR.

0 I a I 5 7 MnO ADDITON (wI.%I BASE COMPOSITION VFIIG.4

PLANAR MECHANICAL 0.5 wf. MnO

PLANAR COUPLING COEFFICIENT.

OJ ay,

0 3 5 7 NiO ADDITION (WI.%I BASE COMPOSITION P b (M va 2/3 037s bsn 'ozss INVENTORS HIROMU OUCHI MASAMITSU NISIHIDA United States Patent3,425,944 PIEZOELECTRIC CERAMIC COMPOSITIONS Hiromu Ouchi, Toyonaka-shi,Osaka-fu, and Masamitsu Nishida, Osaka-shi, Osaka-fu, Japan, assignorsto Matsushita Electric Industrial Co., Ltd., Osaka, Japan Filed Dec. 14,1965, Ser. No. 513,798 US. Cl. 252---62.9 Int. C1. C04!) 35/28, 35/36 6Claims ABSTRACT OF THE DISCLOSURE Piezoelectric ceramic compositions ofthe ternary systfil'n Pb(Mg Nb )O -PbTiO -PbZrO combined MnO and NiOadditives for enhanced mechanical quality factor and couplingcoefficient. These compositions have utility in various transducerapplications.

The ceramic bodies materialized by the present invention exist basicallyin the following solid solution comprising the ternary system Pb(Mg Nb)O -PbTiO PbZrO modified with combined MnO and NiO additives. Apolycrystalline material composed of Pb(Mg Nb O -PbTiO -PbZr'O will bereferred to as PCM.

The use of piezoelectric materials in various transducer applications inthe production, measurement and sensing of sound, shock, vibration,pressure, etc., have increased greatly in recent years. Both crystal andceramic types of transducers have been widely used. But, because oftheir potentially lower cost and facility in the fabrication of ceramicswith various shapes and sizes and their greater durability for hightemperature and/ or for humidity than that of crystalline substancessuch as Rochelle salt, piezoelectric ceramics materials have recentlycome to importance in various transducer applications.

The piezoelectric characteristics of ceramics required apparently varywith species of applications. For example, electromechanical transducerssuch as phonograph pickup and microphone require piezoelectric ceramicscharacterized a substantially high electromechanical couplingcoefiicient and dielectric constant. On the other hand, it is desired tofilter applications of piezoelectric ceramics that the material exhibita higher value of mechanical quality factor and high electromechanicalcoupling coefficient. Furthermore, ceramic materials require a highstability with temperature and time in resonant frequency and in otherelectrical properties.

As more promising ceramics for these requirements, lead titanate-leadzirconate is in Wide use up to now. However, it is difiicult to get avery high mechanical quality factor combined with high planar couplingcoefficient in the lead titanate-lead zirconate ceramics.

It is, therefore, the fundamental object of the present invention toprovide a novel and improved piezoelectric ceramic materials whichovercomes at least one of the problems outlined above.

A more specific object of the invention is to provide im- 3,425,944Patented Feb. 4, 1969 proved polycrystalline ceramics characterized byvery high mechanical quality factor combined with high piezoelectriccoupling coefficient.

Another object of the invention is the provision of novel piezoelectricceramic compositions, certain properties of which can be'adjusted tosuit various applications.

A further object of the invention is the provision of improvedelectromechanical transducer utilizing, as the active elements, anelectrostatically polarized body of the novel ceramic compositions.

These objects of the invention and the manner of their attainment willbe readily apparent from a reading of the following description and fromthe accompanying drawing, in which:

FIG. 1 is a cross-sectional view of an electromechanical transducerembodying the present invention.

FIG. 2 is a triangular, compositional diagram of materials utilized inthe present invention.

FIGS. 3 and 4 are a graph showing the effects of amounts of additives onmechanical quality factor (Q and planar coupling coetficient (K,,) ofexemplary compositions accordng to the present invention at 20 C. and 1kc.

Before proceeding with a detailed description of the piezoelectricmaterials contemplated by the invention, their application inelectromechanical transducers will be described with reference to FIGURE1 of the drawings wherein reference character 7 designates, as a whole,an electromechanical transducers having, as its active element, apreferably disc shaped body '1 of piezoelectric ceramic materialsaccording to the present invention.

Body 1 is electrostatically polarized, in a manner hereinafter setforth, and is provided with a pair of electrodes 2 and 3, applied in asuitable manner, on two opposed surfaces thereof. Wire leads 5 and 6 areattached con ductively to the electrodes 2 and 3 respectively by meansof solder 4. When the ceramic is subjected to shock, vibration or othermechanical stress, an electrical output generated can be taken from wireleads 5 and 6. Conversely, as with other piezoelectric transducers,application of electrical voltage to electrodes 5 and '6 will result inmechanical deformation of the ceramic body. It is to be understood thatthe term electromechanical transducer as used herein is taken in itsbroadest sense and includes piezoelectric filter, frequency controldevices, and the like, and that the invention may also be used andadapted to various other applications requiring materials havingdielectric, piezoelectric and/or electrostructive properties. In thecopending US. patent application Ser. No. 450,738 filed Apr. 26, 1965,now Patent No. 3,268,453, the present inventors have disclosed thatternary solid solution of Pb(Mg Nb )O -PbTiO -PbZrO exists in perovskitetype structure and exhibits excellent piezoelectric properties at avicinity of morphotropic compositions. These ternary compositions andtheir piezeoelectric and dielectric properties are also listed in ourpaper, Journal of the American Ceramic Society, December 1965, vol. 48,No. 12, pp. 630-635.

All possible compositions coming within the ternary system P-b(Mg Nb )O-PbTio -PtbZro are represented by the triangular diagram constitutingFIG. 2 of the drawings. Some compositions represented by the diagram,however, does not exhibit high piezoelectricity, and many areelectromechanically active only to a slight degree. The presentinvention is concerned only with those compositions exhibitingpiezoelectric response of appreciable magnitude. As a matter ofconvenience, the planar coupling coeflicient (K of test discs will betaken as a measure of piezoelectric activity; Thus; within the areabounded by lines connecting points ABCDEF, FIG. 2, all compositionspolarized and tested show a planar coupling 3 coefiicient ofapproximately 5% or higher. The compositions in the area of the diagrambounded by lines connecting points GHIKLNO of FIG. 2, exhibit a planarcoupling coefficient of approximately 20% or higher. Particularly thecompositions within the polygonal region 4 (ZrO Mn and NiO, all ofrelatively pure grade (e.g., 0?. grade) are intimately mixed in arubber-lined ball mill with distilled water. In milling the mixture careshould be exercised to avoid, or the proportions of ingredients variedto compensate for, contamination by wear PQRSTU which includescompositions of 500-625 mole of the milling ball or stones. percent ofPb(Mg Nb O 50.0-25.0 mole percent of Following the wet milling, themoisture is dried and PbTiO and 62.5-12.5 mole percent of PbZrO exhibita mixed to assure as homogeneous a mixture as possible. planar couplingcoefiicient of approximately 30% or Thereafter, the mixture, suitablyformed into desired higher. The molar percent of the three components offorms at a pressure of 400 kg./cm. The compacts are compositionsABCDEFGHIKLNOPQRSTU are as folpre-reacted by calcination at atemperature of around lows: 850 C. for 2 hours.

After calcination, the reacted material is allowed to /6 %)0a PbTiOaPbZIOa cool and is then wet milled to a small particle size. Once 815115 M again, care should be exercised to avoid, or the proporg-g tionsof ingredients varied to compensate for, contaminaj 5 tion by wear ofthe milling balls or stones. Depending on 8L3 preference and the shapesdesired the material my be 18.7 81.3 0.0 62 5 M formed into m1x or slipsuitable for pressing, slip casting, 5 251) 20 or extruding, as the casemay be, in accordance with con- 50.0 12.5 37.5

2M 7M ventional ceramic procedures. The sample for wh1ch data 8 aregiven hereinbelow were prepared by mixing 100 grams 1 0f d of the milledpro-sintered mixture with 5 cc. of distilled 28-8 32-8 water. The mixwas then pressed into discs of 20 mm. 1215 :0 0215 25 diameter and 2 mm.thickness at a pressure of 700 kg./ g 3 cm. The pressed discs are firedat a temperature set in 37.5 500 1215 table for 45 minutes of heatingperiod. According to the present invention, there is no need to fire thecom- Furthermore, the compositions near the morphotropic position in anatmosphere of PbO and no special care is phase boundary, particularlyPb(Mg Nb Ti required for the temperature gradient in a furnace com- Zr Oand Pb(Mg Nb Ti Zr O give pared with the prior art. Thus, according tothe present ceramic products having a planar coupling coefficient ofinvention, uniform and excellent piezoelectric ceramic 45% or higher.products can be easily obtained simply by covering the According to thepresent invention it has been discovered samples with an aluminacrucible. that an addition of combined additives of nickel oxide and 35The sintered ceramics are polished on both surfases to manganese oxideimproves the Q and K of the ternary the thickness of one millimeter. Thepolished disc surfaces solid solution defined by the polygonal areaABCDEF in may then be coated with silver paint and fired to form FIG. 2more extensively than a single addition of nickel silver electrodes.Finally, the discs are polarized while oxide or manganese oxide.Operable additive combination immersed in a bath of silicone oil at 100C. A voltage comprises 0.1 to 5 weight percent of nickel oxide (NiO)gradient of D-C kv. per mm. is maintained for one hour, and 0.1 to 5weight percent of manganese oxide (MnO and the discs are field-cooled toroom temperature in It is necessary for obtaining high Q and high K thatthirty minutes. said additive combination has 0.2 to 10 of a weightratio The piezoelectric and dielectric properties of the polarof nickeloxide to manganese oxide. Operable weight perized specimen have beenmeasured at 20 C. in a relative cent of said combination is not morethan 6%. An addihumidity of and at a frequency of l kc. A measuretion ofsaid combination more than 7 weight percent rement of piezoelectricproperties was made by the IRE duces slightly the K and clearly the Q ofthe ternary standard circuit and the planar coupling coeflicient wassolid solution. A preferable improvement in the K and determined by theresonant to antiresonant frequency Q of ternary solid solution definedby and included method. Examples of specific ceramic compositionsacwithin the polygonal area PQRSTU in FIGURE 2 can 50 cording to thisinvention and various pertinent electrobe obtained by employing 0.5 to 1weight percent of addimechanical and dielectric properties thereof aregiven in tive combination having 0.5 to 2.0 of the weight ratio of tableand some of their Value are Plotted in FIGURES NiO to MnO Desirableefleet of mo specified ddi- 3 and 4 to show the variation withadditives. Compositions will be readily understood b th ifi d examplestions Without additives and with only one additive are indicated in thefollowing table, also given in table and FIGURES 34 for purpose of Thecomposition described herein may be prepared in comparison. From tableit will be readily evident that accordance with various well knownceramic procedures. all exemplary composition modified With an additionof A preferred method, however, hereinafter more fully both t0 5 Weight136N611t of nickel OXide and i0 5 described, consists in the use of PbOor Pb O MgO or Weight Percent of manganese Oxide are Characteriled yMgCO Nb O TiO M110 and NiO, very high mechanical quality factor, highplanar coupling, The starting materials, viz., lead oxide (PbO),magrelatively high dielectric constant and low dissipation nesia (MgO),niobia (Nb 0 titania (T10 zirconia factor, all of TABLE Intendedcompositioni F 24 hours after poling Example Additives, in W l i 1 3g,Mechanical Planar Dielectric Dissipation No. Base composition weightpercent 0. quality coupling constant D, in percent factor, QM coefi.K,,, at 1 kc. P.S. at 1 kc. P.S. MnO NiO in percentgi/aNbm)o.aTi0.a7sZro.z50z.. None None 1,280 89 50.2 1,589 1. 75 g1/a2/a)o.a75 o m ro 250a. 1. 0 ,240 62.0 1,930 1.05 3..Pb(Mg1/aNb2/a)0.a7sT10.s7sZro 2503.- O. 1 1,260 265 52. 0 1, 512 0. 82

g1/a b2/a)o.an omtZm.7503 0.1 1.0 1, 200 378 59.5 1,704 0.76 g1/abr/a)0.a7s io.z75Zro.250s 0. 2 260 626 54. 0 1, 435 0. 34 g1/:2/3)0.a75Ti0.mZIoJsOa 0.2 1.0 1,240 752 58.6 1, 520 0.20 7..Pb(Mg1/3Nb2/3)0.a'ltTiumszl'ogsoa.. O. 5 1,260 1, 044 52. 7 1, 131 0. 458.. Pb(MEi/aNba/Oo.a7sTi Zr0.2503. 0.5 1.0 1,240 1,842 55.1 1,103 0.409.- Pb( gl/JNbZ/S)0,}15T10J75ZTOJ503 1. 0 260 1, 530 48. 3 907 0. 89

TAB LE-Continued Intended composition 24 hours after paling FiringExample Additives, in temp., Mechanical Planar Dielectric DissipationNo. Base composition weight percent 0. quality coupling constant D, inpercent factor, Q coefi. K, at 1 kc. RS. at 1 kc. RS. M110 N in percent10 l/3 2/3)0.375T10.375ZTOJ5O3 1. 0 1. 0 1, 240 1, 548 51. 1 877 0. 8811 Pb(Mgr/aNbz/ah.a7sTl0.a7s Io.2sO3. 3. 0 1, 240 753 39. 2 695 3. 38guaNbm)o.a1sTio.a1sZro.2sO:- 3. 0 1. O 1, 240 938 38. 8 643 3. 35Pb(MguaNbz/shsn'llo.a75ZIo 250a. 5. 0 1, 220 386 36. 0 704 7. 18Pb(Mg1/s b2/a)o.arsTiom ro 250:- 5.0 1.0 1, 240 505 34. 4 633 9.20 b(g1/3 2/3)D.375' 10.375 '0 250a. 7. 0 1, 200 261 32. 6 700 11. 95 g1/ab2/s)o.s:5T}o.a1sZro 2503-- 7. 0 1. 0 1, 220 186 31. 4 911 15. 7sPb(Mg1/sNb2/a)o.s75T1o.s75Zlo 2502. 0. 1 1, 260 81 54. 5 1, 712 1. 88 b(gi/a b2/a)o.e1sT1 u 31 Zr r503. 0. 5 0.1 1, 260 1, 712 53. 6 1,089 0.49Pb(Mgr/s I/s)o.s75 }0.a7s ro 250s. 0- 2 1, 260 75 57. 7 1, 762 1. 93Pb(Mg1 3 bz/3)n,a75T1 75Zr0 2503" O. 5 U. 2 1, 260 1, 752 54. 7 1,058 O.47 Pb(Mgz/sNbz s)a.a75T1o 375Zro 250a- 0. 5 1, 260 88 64. 4 1, 843 1. 27

P13 (Mg1/3Nb2/3)u 375Tlo 375Z10 250:. 0. 5 0. 5 1, 260 2, 051 55. 3 9320. 35 P1'J(1V1g1/3N 2/3)0.375Tl0 3 Zro n03. 0. 5 1. O 1, 240 1, 842 55.1 1, 103 0.40 Pb(Mg /3Nb2/a)o.s7sTlo.375ZIo.1503. 3- 0 1, 240 93 61. 22, 434 1. Pb(MgllsNbz/a)0,375'110375Z10J50m U. 5 3. 0 1, 240 1, 780 54.6 1, 410 0. 45 Pb(Mg /sNb2/3)o.375T1u.a15Zl'o.2503. c 5. 0 1, 240 10358. 3 2, 654 1. 22

Pb (Mg1/3Nbz/3)o 375Tl0 375ZI0J503. U. 5 5. O 1, 240 1, 804 50. 2 1, 6920. 45 Pb(Mg1/3Nb:/3)o, 75T10 a15Zro.z503 7. 0 1, 240 1 0 56. 9 2, 678 1.30 Pb(Mg1/sN 2/a)o.a1.T1 375Z1'0J503- 0. 5 7. 0 1, 240 1, 477 so. 2 1,743 0. 47 Pb( 8r/a b2/3)0A375 10.4375 10J25 L e None 260 127 4 713 58Pb(Mg1/3N1J2/3)0A375T103117521012503 0- 5 0 108 39. 0 1, 846 1. 27 Pb(Mg/3Nbg/3)0,4 75Tlu4 75Z1'0J2503. 0. 5 0. 5 1, 260 1, 476 41. 2 1, 734 0.Pb(Mg Nbg )n 4 75T1u rmzlo 1250a. 1. U 0. 5 1, 260 1, 639 38. O 1, 5340. 73 Pb(Mg Nbz )o,ravsTloAmZlonzsOs 1. 0 1, 260 118 42- 2 1, 870 1. 06Pb(Mg1/3Nbz/3)0,4375'1210,4375Z!0.12503. 0- 5 1. U 1, 260 1, 742 39. 41, 616 0. 27 Pb(Mg Nbm)nJnTiusnZronOa; None None 1, 300 140 27. 1 452 0.90 Pb(Mg1/3Nb:/3)0 z5T1o szsZlo 2505. c 0- 5 1, 300 1, 1 28. 5 393 0. 41

Pb(Mg1/3Nbz/3)o mT1o mZro 2503. 0. 5 0. 5 300 1,324 38. 9 425 O. 53Pb(Mg Nbg z5Tlo 5252M 2 03. 1. 0 1, 300 1, 227 26- 8 341 0. 82Pb(Mg1/3Nb2/3)u 125Tiu,sz5Z1o z503 1. 0 0. 5 1, 300 1, 518 27. 1 376 0.76

which properties are important to the use of piezoelectric compositionsin filter applications. Example Nos. 1 to 29, Example Nos. 30 to 35 andExample Nos. 36 to listed in table correspond to a composition definedby X, Y and Z in FIGURE 2, respectively. FIGURE 3 indicate the eifect ofamounts of MnO addition on mechanical quality factor (Q and planarcoupling coefficient (K,,) of exemplary base compositions having 1.0weight percent of NiO addition. From this figure it will be obvious thatthe compositions modified with combined NiO and MnO additives exhibit anoticeable improvement of mechanical quality factor and planar couplingcoefficient as compared with that of the composition with a singleaddition of M1102.

FIGURE 4 indicate the eifect of amounts of NiO addition on' mechanicalquality factor (Q and planar coupling coefficient (K,,) of exemplarybase compositions having 0.5 weight percent of Mn0 addition. From thisfigure it will be obvious that the compositions modified with combinedMnO and NiO additives exhibit a remarkable improvement of mechanicalquality factor as compared with that of the composition with a singleaddition of NiO. Planar coupling coefficient of compositions modifiedwith combined MnO and NiO additives show a somewhat lowered value, but,these values are still higher than that of basic composition withoutadditive. Improvements of mechanical quality factor for another basecomposition are also seen for the Example Nos. 32, 33, 35, 38 and 40 intable. From the foregoing table and figures, the values of mechanicalquality factor, planar coupling coefficient and dielectric constant canbe adjusted to suit various applications by selecting the basecomposition and amounts of combined additives.

In addition to the superior properties showed above, compositionaccording to the present invention yield ceramics of good physicalquality and which polarize well. It will be understood from theforegoing that the ternary solid solution Pb(Mg Nb )O -PbTiO -PbZrOmodified with combined MnO and NiO additives form a excellentpiezoelectric ceramic body.

What is claimed is:

1. A piezoelectric ceramic composition consisting essentially of a basematerial expressed by the general formula Pb(Mg Nb Ti Zr O wherex+y+z=1, and having a composition within a polygonal region ABCDEF inthe triangular composition diagram of FIGURE 2 and 30 0.1 to 6 Weightpercents of additive combination of nickel oxide and manganese oxide,said ceramic composition having 0.2 to 10 weight ratio of nickel oxideto manganese oxide, the molar ratio of the three components of eachvertices are as follows:

999 999 OUIH ON ooosooi olQ 3. A piezoelectric ceramic compositionconsisting essentially of a base material selected from those defined byand included within the polygonal area PQRSTU of the triangularcomposition diagram in FIGURE 2 and 0.1 to 6 weight percents of additivecombination of nickel oxide and manganese oxide, said ceramiccomposition having 0.2 to 10 weight ratio of nickel oxide to manganese0. 375 O. 125 0. 250 O. 250 0. 250 0. 625 O 0625 O. 3125 0. 625 O. 0625O. 500 0. 4375 U O. 375 0. 500 0. 125

4. A piezoelectric transducer element comprising an electrostaticallypolarized solid solution ceramic consisting essentially of a materialselected from the polygonal area PQRSTU of FIGURE 2 and 1.5 Weightpercents of additive combination of nickel oxide and manganese oxide,said ceramic composition having 0.5 to 2.0 of a weight ratio of nickeloxide to manganese oxide.

5. A piezoelectric ceramic composition consisting essentially of 99Weight percent Pb(Mg Nb "H 8 Zr O 0.5 Weight percent nickel oxide (NiO)and 0.5 weight percent manganese oxide (MnO 6. A piezoelectri ceramiccomposition consisting essentially of 99 weight percent Pb(Mg Nb T104375Z1'0 125O3, 0.5 weight percent nickel oxide (NiO) and 0.5 weightpercent manganese oxide (MnO References Cited UNITED STATES PATENTS3,068,177 12/1962 Sugden 252-62.9 3,268,453 8/1966 Ouchi et al. 25262.9

TOBIAS E. LEVOW, Primary Examiner.

ROBERT D. EDMONDS, Assistant Examiner.

US. Cl. X.R. 106-39

